Switch to use GPU instead of inference client

Move environment variable querying code out of the Gradio UI-construction functions all the way to the root of the application, `app.py`

Move environment variable querying code out of the inference functions

Add documentation

Reorganize structure for even less code clutter; `app.py` is greatly slimmed down

Add AI-generated chat sample

Add automatic speech recognition (ASR) sample

Add text-to-speech (TTS) sample